Technical Field
The present disclosure relates to a method for temperature drift compensation of a temperature measurement device using a thermocouple.
Description of the Related Art
Conventionally, a temperature measurement device using a thermocouple is provided with a compensation circuit to compensate for influence of the temperature of the surroundings, which is unnecessary. The compensation circuit is implemented by providing a reference voltage generating circuit to an input terminal or providing a temperature sensor and a multiplexer to the input terminal. In particular, the temperature sensor and multiplexer are added to reduce complexity and errors of providing the reference voltage generating circuit.
For a temperature measurement device using a temperature sensor and multiplexer, when the temperature of the place where the temperature measurement device is installed changes, the conventional technology produces an error in measuring temperature due to temperature drift.
Herein, drift refers to change in a measured value with a change of the environment. The most significant drift observed by various sensors is typically caused by change in temperature of the surroundings, which is called “temperature drift.”
To maintain high precision in temperature measurement, a temperature compensation function needs to be provided or a sensor needs to be installed in a pyrostat so as to be maintained at a constant temperature. In addition to the temperature drift, aging drift, which results from aging of an element in use, is also considered important. This drift is an important element in determining the period of correction of a sensor or guage.
The thermocouple is a device for measuring temperature in a wide range using the Seebeck effect. Thermocouples are used in a power plant, steel mill, and the like, and are widely used in extreme situations due to high durability thereof.
A temperature measurement device using the thermocouple measures a temperature using electromotive force generated in the thermocouple. Herein, the measured temperature has a value measured with respect to 0° C. Accordingly, the temperature around a part of the measurement device to which the thermocouple is actually connected is measured and added to the measured value. This compensation is referred to as reference junction compensation or cold junction compensation.
Conventionally, to compensate for the temperature drift, a separate temperature measurement circuit is implemented in the temperature measurement device, or the temperature around a part to which a product is mounted is maintained to be constant.
However, the conventional temperature measurement device using a thermocouple needs to perform the reference junction compensation to measure a temperature. However, this procedure has a limit in compensating for an error resulting from the temperature drift. That is, an external cause of temperature change sensed by a thermistor for reference junction compensation and an internal cause of temperature change are not delivered with a constant ratio.
Accordingly, to overcome such limit, a separate means to correct the temperature drift is needed. Such means typically requires a separate temperature measurement element capable of sensing change in temperature of the surroundings.